Caltech News tagged with "quantum"http://www.caltech.edu/news/tag_ids/48/rss.xml
enPhysics Boosts Artificial Intelligence Methodshttp://www.caltech.edu/news/physics-boosts-artificial-intelligence-methods-80127
<div class="field field-name-field-images field-type-file field-label-hidden"><div class="field-items"><div class="field-item even"><div class="ds-1col file file-image file-image-jpeg view-mode-full_grid_9 clearfix ">
<img src="http://s3-us-west-1.amazonaws.com/www-prod-storage.cloud.caltech.edu/styles/article_photo/s3/MSpiropulu-Oct19-NEWS-WEB.jpg?itok=pvrHkJ3B" alt="Higgs boson event" /><div class="field field-name-field-caption field-type-text field-label-hidden"><div class="field-items"><div class="field-item even">Higgs "di-photon" event candidate from Large Hadron Collider data collisions overlaid with a schematic of a wafer of quantum processors.</div></div></div><div class="field field-name-credit-sane-label field-type-ds field-label-hidden"><div class="field-items"><div class="field-item even">Credit: LHC Image: CERN/CMS Experiment; Composite: M. Spiropulu (Caltech)</div></div></div></div></div></div></div><div class="field field-name-body field-type-text-with-summary field-label-hidden"><div class="field-items"><div class="field-item even"><p>Researchers from Caltech and the University of Southern California (USC) report the first application of quantum computing to a physics problem. By employing quantum-compatible machine learning techniques, they developed a method of extracting a rare Higgs boson signal from copious noise data. Higgs is the particle that was predicted to imbue elementary particles with mass and was discovered at the Large Hadron Collider in 2012. The new quantum machine learning method is found to perform well even with small datasets, unlike the standard counterparts.</p><p>Despite the central role of physics in quantum computing, until now, no problem of interest for physics researchers has been resolved by quantum computing techniques. In this new work, the researchers successfully extracted meaningful information about Higgs particles by programming a quantum annealer—a type of quantum computer capable of only running optimization tasks—to sort through particle-measurement data littered with errors. Caltech's Maria Spiropulu, the Shang-Yi Ch'en Professor of Physics, conceived the project and collaborated with Daniel Lidar, pioneer of the quantum machine learning methodology and Viterbi Professor of Engineering at USC who is also a Distinguished Moore Scholar in Caltech's divisions of Physics, Mathematics and Astronomy and Engineering and Applied Science.</p><p>The quantum program seeks patterns within a dataset to tell meaningful data from junk. It is expected to be useful for problems beyond high-energy physics. The details of the program as well as comparisons to existing techniques are detailed in a <a href="http://resolver.caltech.edu/CaltechAUTHORS:20170802-103416956">paper</a> published on October 19 in the journal <em>Nature</em>.</p><p>A popular computing technique for classifying data is the neural network method, known for its efficiency in extracting obscure patterns within a dataset. The patterns identified by neural networks are difficult to interpret, as the classification process does not reveal how they were discovered. Techniques that lead to better interpretability are often more error prone and less efficient.</p><p>"Some people in high-energy physics are getting ahead of themselves about neural nets, but neural nets aren't easily interpretable to a physicist," says USC's physics graduate student Joshua Job, co-author of the paper and guest student at Caltech. The new quantum program is "a simple machine learning model that achieves a result comparable to more complicated models without losing robustness or interpretability," says Job.</p><p>With prior techniques, the accuracy of classification depends strongly on the size and quality of a training set, which is a manually sorted portion of the dataset. This is problematic for high-energy physics research, which revolves around rare events buried in large amount of noise data. "The Large Hadron Collider generates a huge number of events, and the particle physicists have to look at small packets of data to figure out which are interesting," says Job. The new quantum program "is simpler, takes very little training data, and could even be faster. We obtained that by including the excited states," says Spiropulu.</p><p>Excited states of a quantum system have excess energy that contributes to errors in the output. "Surprisingly, it was actually advantageous to use the excited states, the suboptimal solutions," says Lidar.</p><p>"Why exactly that's the case, we can only speculate. But one reason might be that the real problem we have to solve is not precisely representable on the quantum annealer. Because of that, suboptimal solutions might be closer to the truth," says Lidar.</p><p>Modeling the problem in a way that a quantum annealer can understand proved to be a substantial challenge that was successfully tackled by Spiropulu's former graduate student at Caltech, Alex Mott (PhD '15), who is now at DeepMind. "Programming quantum computers is fundamentally different from programming classical computers. It's like coding bits directly. The entire problem has to be encoded at once, and then it runs just once as programmed," says Mott.</p><p>Despite the improvements, the researchers do not assert that quantum annealers are superior. The ones currently available are simply "not big enough to even encode physics problems difficult enough to demonstrate any advantage," says Spiropulu.</p><p>"It's because we're comparing a thousand qubits—quantum bits of information—to a billion transistors," says Jean-Roch Vlimant, a postdoctoral scholar in high energy physics at Caltech. "The complexity of simulated annealing will explode at some point, and we hope that quantum annealing will also offer speedup," says Vlimant.</p><p>The researchers are actively seeking further applications of the new quantum-annealing classification technique. "We were able to demonstrate a very similar result in a completely different application domain by applying the same methodology to a problem in computational biology," says Lidar. "There is another project on particle-tracking improvements using such methods, and we're looking for new ways to examine charged particles," says Vlimant.</p><p>"The result of this work is a physics-based approach to machine learning that could benefit a broad spectrum of science and other applications," says Spiropulu. "There is a lot of exciting work and discoveries to be made in this emergent cross-disciplinary arena of science and technology, she concludes.</p><p>This project was supported by the United States Department of Energy, Office of High Energy Physics, Research Technology, Computational HEP; and Fermi National Accelerator Laboratory as well as the National Science Foundation. The work was also supported by the AT&amp;T Foundry Innovation Centers through INQNET (INtelligent Quantum NEtworks and Technologies), a program for accelerating quantum technologies.</p><p><em>Written by Mark H. Kim </em></p></div></div></div><div class="field field-name-field-pr-links field-type-link-field field-label-above"><div class="field-label">Related Links:&nbsp;</div><div class="field-items"><div class="field-item even"><a href="http://inqnet.caltech.edu/news.html" class="pr-link">INQNET News</a></div></div></div>Wed, 18 Oct 2017 17:01:25 +0000wclavin80127 at http://www.caltech.eduCaltech Computer Scientist Thomas Vidick Named CIFAR Azrieli Global Scholarhttp://www.caltech.edu/news/caltech-computer-scientist-thomas-vidick-named-cifar-azrieli-global-scholar-80084
<div class="field field-name-field-subtitle field-type-text field-label-hidden"><div class="field-items"><div class="field-item even">Vidick, who specializes in quantum computing and quantum cryptography, will be awarded $100,000 in research support from the Canadian Institute for Advanced Research</div></div></div><div class="field field-name-news-writer field-type-ds field-label-inline clearfix"><div class="field-label">News Writer:&nbsp;</div><div class="field-items"><div class="field-item even">Robert Perkins</div></div></div><div class="field field-name-field-images field-type-file field-label-hidden"><div class="field-items"><div class="field-item even"><div class="ds-1col file file-image file-image-jpeg view-mode-full_grid_9 clearfix ">
<img src="http://s3-us-west-1.amazonaws.com/www-prod-storage.cloud.caltech.edu/styles/article_photo/s3/Vidick-Thomas_6349_CIFAR-NEWS-WEB.jpg?itok=ZPcq5_-c" alt="Vidick" /><div class="field field-name-field-caption field-type-text field-label-hidden"><div class="field-items"><div class="field-item even">Thomas Vidick</div></div></div><div class="field field-name-credit-sane-label field-type-ds field-label-hidden"><div class="field-items"><div class="field-item even">Credit: Caltech</div></div></div></div></div></div></div><div class="field field-name-body field-type-text-with-summary field-label-hidden"><div class="field-items"><div class="field-item even"><p>Caltech computer scientist Thomas Vidick has been named an Azrieli Global Scholar by the Canadian Institute for Advanced Research. Vidick, an associate professor of computing and mathematical sciences in the Division of Engineering and Applied Science, was one of 15 early career researchers to receive the two-year appointment.</p><p>According to the Azrieli Global Scholar website, the program "funds and supports researchers within five years of their first academic appointment, helping them build research networks and develop leadership skills." Each of the new scholars will receive $100,000 (Canadian) in research support and will become a part of one of CIFAR's 12 research programs for two years.</p><p>Vidick joined Caltech's faculty in 2014. His research focuses on quantum computing, both on how to make it more efficient and how to encrypt information using quantum systems to transmit data more securely than through classical systems. He recently received an <a href="http://eas.caltech.edu/news/825">Air Force Office of Scientific Research Young Investigator Award</a> and an <a href="http://eas.caltech.edu/news/828">NSF Faculty Early Career Development Award</a>. Vidick also teaches an <a href="http://www.caltech.edu/news/caltech-offers-open-online-course-quantum-cryptography-52456">open online course in quantum cryptography</a>. </p></div></div></div>Sun, 15 Oct 2017 20:58:58 +0000rperkins80084 at http://www.caltech.eduFirst On-Chip Nanoscale Optical Quantum Memory Developedhttp://www.caltech.edu/news/first-chip-nanoscale-optical-quantum-memory-developed-79591
<div class="field field-name-field-subtitle field-type-text field-label-hidden"><div class="field-items"><div class="field-item even">Smallest-yet optical quantum memory device is a storage medium for optical quantum networks with the potential to be scaled up for commercial use</div></div></div><div class="field field-name-news-writer field-type-ds field-label-inline clearfix"><div class="field-label">News Writer:&nbsp;</div><div class="field-items"><div class="field-item even">Robert Perkins</div></div></div><div class="field field-name-field-images field-type-file field-label-hidden"><div class="field-items"><div class="field-item even"><div class="ds-1col file file-image file-image-jpeg view-mode-full_grid_9 clearfix ">
<img src="http://s3-us-west-1.amazonaws.com/www-prod-storage.cloud.caltech.edu/styles/article_photo/s3/Faraon%20quantum.jpg?itok=DGz-9bW2" alt="Faraon quantum" /><div class="field field-name-field-caption field-type-text field-label-hidden"><div class="field-items"><div class="field-item even">Artist&#039;s representation of Faraon&#039;s quantum memory device.</div></div></div><div class="field field-name-credit-sane-label field-type-ds field-label-hidden"><div class="field-items"><div class="field-item even">Credit: Ella Maru Studio</div></div></div></div></div></div></div><div class="field field-name-body field-type-text-with-summary field-label-hidden"><div class="field-items"><div class="field-item even"><p>For the first time, an international team led by engineers at Caltech has developed a computer chip with nanoscale optical quantum memory.</p><p>Quantum memory stores information in a similar fashion to the way traditional computer memory does, but on individual quantum particles—in this case, photons of light. This allows it to take advantage of the peculiar features of quantum mechanics (such as superposition, in which a quantum element can exist in two distinct states simultaneously) to store data more efficiently and securely.</p><p>"Such a device is an essential component for the future development of optical quantum networks that could be used to transmit quantum information," says <a href="http://eas.caltech.edu/people/faraon">Andrei Faraon</a> (BS '04), assistant professor of applied physics and materials science in the Division of Engineering and Applied Science at Caltech, and the corresponding author of a paper describing the new chip.</p><p>The study appeared online ahead of publication by <em>Science</em> magazine on August 31.</p><p>"This technology not only leads to extreme miniaturization of quantum memory devices, it also enables better control of the interactions between individual photons and atoms," says Tian Zhong, lead author of the study and a Caltech postdoctoral scholar. Zhong is also an acting assistant professor of molecular engineering at the University of Chicago, where he will set up a laboratory to develop quantum photonic technologies in March 2018.</p><p>The use of individual photons to store and transmit data has long been a goal of engineers and physicists because of their potential to carry information reliably and securely. Because photons lack charge and mass, they can be transmitted across a fiber optic network with minimal interactions with other particles.</p><p>The new quantum memory chip is analogous to a traditional memory chip in a computer. Both store information in a binary code. With traditional memory, information is stored by flipping billions of tiny electronic switches either on or off, representing either a 1 or a 0. That 1 or 0 is known as a bit. By contrast, quantum memory stores information via the quantum properties of individual elementary particles (in this case, a light particle). A fundamental characteristic of those quantum properties—which include polarization and orbital angular momentum—is that they can exist in multiple states at the same time. This means that a quantum bit (known as a qubit) can represent a 1 and a 0 at the same time.</p><p>To store photons, Faraon's team created memory modules using optical cavities made from crystals doped with rare-earth ions. Each memory module is like a miniature racetrack, measuring just 700 nanometers wide by 15 microns long—on the scale of a red blood cell. Each module was cooled to about 0.5 Kelvin—just above Absolute Zero (0 Kelvin, or -273.15 Celsius)—and then a heavily filtered laser pumped single photons into the modules. Each photon was absorbed efficiently by the rare-earth ions with the help of the cavity.</p><p>The photons were released 75 nanoseconds later, and checked to see whether they had faithfully retained the information recorded on them. Ninety-seven percent of the time, they had, Faraon says.</p><p>Next, the team plans to extend the time that the memory can store information, as well as its efficiency. To create a viable quantum network that sends information over hundreds of kilometers, the memory will need to accurately store data for at least one millisecond. The team also plans to work on ways to integrate the quantum memory into more complex circuits, taking the first steps toward deploying this technology in quantum networks.</p><p>The study is titled <a href="http://resolver.caltech.edu/CaltechAUTHORS:20170815-100238435">"Nanophotonic rare-earth quantum memory with optically controlled retrieval."</a> Other Caltech coauthors include postdoctoral researcher John G. Bartholomew; graduate students Jonathan M. Kindem (MS '17), Jake Rochman, and Ioana Craiciu (MS '17); and former graduate student Evan Miyazono (MS '15, PhD '17). Additional authors are from the University of Verona in Italy; the University of Parma in Italy; the National Institute of Standards and Technology in Colorado; and the Jet Propulsion Laboratory, which is managed for NASA by Caltech. This research was funded by the National Science Foundation, the Air Force Office of Scientific Research, and the Defense Advanced Research Projects Agency.</p></div></div></div><div class="field field-name-field-pr-links field-type-link-field field-label-above"><div class="field-label">Related Links:&nbsp;</div><div class="field-items"><div class="field-item even"><a href="http://www.caltech.edu/content/creating-new-quantum-building-blocks" class="pr-link">Creating New Quantum Building Blocks</a></div></div></div>Sun, 10 Sep 2017 21:59:03 +0000rperkins79591 at http://www.caltech.eduDesigning Computer Software of the Futurehttp://www.caltech.edu/news/designing-computer-software-future-79114
<div class="field field-name-field-subtitle field-type-text field-label-hidden"><div class="field-items"><div class="field-item even">Fernando Brandão is developing quantum algorithms for optimization problems</div></div></div><div class="field field-name-news-writer field-type-ds field-label-inline clearfix"><div class="field-label">News Writer:&nbsp;</div><div class="field-items"><div class="field-item even">Whitney Clavin</div></div></div><div class="field field-name-field-images field-type-file field-label-hidden"><div class="field-items"><div class="field-item even"><div class="ds-1col file file-image file-image-jpeg view-mode-full_grid_9 clearfix ">
<img src="http://s3-us-west-1.amazonaws.com/www-prod-storage.cloud.caltech.edu/styles/article_photo/s3/Quantum_Computing_NewStudy-638-NEWS-WEB.jpg?itok=FAwaMCnG" alt="Computer chip illustration " /><div class="field field-name-field-caption field-type-text field-label-hidden"><div class="field-items"><div class="field-item even">Illustration of a quantum computer chip.</div></div></div><div class="field field-name-credit-sane-label field-type-ds field-label-hidden"><div class="field-items"><div class="field-item even">Credit: iStock </div></div></div></div></div></div></div><div class="field field-name-body field-type-text-with-summary field-label-hidden"><div class="field-items"><div class="field-item even"><p>Quantum computers of the future hold promise for solving complex problems more quickly than ordinary computers. For example, they can factor large numbers exponentially faster than classical computers, which would allow them to break codes in the most commonly used cryptography system. There are other potential applications for quantum computers, too, such as solving complicated chemistry problems involving the mechanics of molecules. But exactly what types of applications will be best for quantum computers, which still may be a decade or more away from becoming a reality, is still an open question.</p><p>In a new Caltech study, accepted by the Institute of Electrical and Electronics Engineers (IEEE) 2017 Symposium on Foundations of Computer Science, researchers have demonstrated that quantum computing could be useful for speeding up the solutions to "semidefinite programs," a widely used class of optimization problems. These programs include so-called linear programs, which are used, for example, when a company wants to minimize the risk of its investment portfolio or when an airline wants to efficiently assign crews to its flights.</p><p>The study presents a new quantum algorithm that could speed up solutions to semidefinite problems, sometimes exponentially. Quantum algorithms are sets of instructions that tell quantum computers what to do to solve problems.</p><p>"One of the goals of quantum computing is to speed up computations to levels that far exceed what classical computers can do," says <a href="https://www.pma.caltech.edu/content/fernando-brandao">Fernando Brandão</a>, the Bren Professor of Theoretical Physics at Caltech. Brandão's co-author is Krysta Svore of Microsoft, which partially funded the study.</p><p>The new quantum algorithm would, in particular, greatly speed up semidefinite programs that are used to learn unknown quantum states. Brandão says that this type of "quantum learning" problem is faced by researchers who study large quantum systems in a variety of different systems such as superconducting qubits, which are quantum information units similar to computer bits that would operate based on superconducting technology. The semidefinite programs are used to give a description of how the quantum matter is behaving, and this, in turn, allows the researchers to better understand the bizarre states of the subatomic world.</p><p>"This type of application is a good candidate for use in quantum computing," says Brandão. "We are still far from knowing all the applications of quantum computing, and that's part of the excitement—there are possibilities we haven't even dreamed of yet."</p><p>The study, titled, <a href="http://resolver.caltech.edu/CaltechAUTHORS:20170726-063707920">"Quantum Speed-ups for Semidefinite Programming,"</a> was funded by Microsoft, the National Science Foundation, and Caltech.</p></div></div></div>Tue, 25 Jul 2017 18:37:27 +0000wclavin79114 at http://www.caltech.eduNew Quantum Liquid Crystals May Play Role in Future of Computershttp://www.caltech.edu/news/new-quantum-liquid-crystals-may-play-role-future-computers-54788
<div class="field field-name-news-writer field-type-ds field-label-inline clearfix"><div class="field-label">News Writer:&nbsp;</div><div class="field-items"><div class="field-item even">Whitney Clavin</div></div></div><div class="field field-name-field-images field-type-file field-label-hidden"><div class="field-items"><div class="field-item even"><div class="ds-1col file file-image file-image-jpeg view-mode-full_grid_9 clearfix ">
<img src="http://s3-us-west-1.amazonaws.com/www-prod-storage.cloud.caltech.edu/styles/article_photo/s3/DHsieh-Isotropic-and-LiquidCrystal_Optical-Response-CB-NEWS-WEB.jpg?itok=LQlxQesq" alt="Patterns from atomic crystals; At right, 3-D quantum liquid crystal" /><div class="field field-name-field-caption field-type-text field-label-hidden"><div class="field-items"><div class="field-item even">These images show light patterns generated by a rhenium-based crystal using a laser method called optical second-harmonic rotational anisotropy. At left, the pattern comes from the atomic lattice of the crystal. At right, the crystal has become a 3-D quantum liquid crystal, showing a drastic departure from the pattern due to the atomic lattice alone. </div></div></div><div class="field field-name-credit-sane-label field-type-ds field-label-hidden"><div class="field-items"><div class="field-item even">Credit: Hsieh Lab/Caltech</div></div></div></div></div></div></div><div class="field field-name-body field-type-text-with-summary field-label-hidden"><div class="field-items"><div class="field-item even"><p>Physicists at the <a href="http://iqim.caltech.edu/">Institute for Quantum Information and Matter</a> at Caltech have discovered the first three-dimensional quantum liquid crystal—a new state of matter that may have applications in ultrafast quantum computers of the future.</p><p>"We have detected the existence of a fundamentally new state of matter that can be regarded as a quantum analog of a liquid crystal," says Caltech assistant professor of physics <a href="https://pma.caltech.edu/content/david-hsieh">David Hsieh</a>, principal investigator on a new study describing the findings in the April 21 issue of <em>Science</em>. "There are numerous classes of such quantum liquid crystals that can, in principle, exist; therefore, our finding is likely the tip of an iceberg."</p><p>Liquid crystals fall somewhere in between a liquid and a solid: they are made up of molecules that flow around freely as if they were a liquid but are all oriented in the same direction, as in a solid. Liquid crystals can be found in nature, such as in biological cell membranes. Alternatively, they can be made artificially—such as those found in the liquid crystal displays commonly used in watches, smartphones, televisions, and other items that have display screens.</p><p>In a "quantum" liquid crystal, electrons behave like the molecules in classical liquid crystals. That is, the electrons move around freely yet have a preferred direction of flow. The first-ever quantum liquid crystal was discovered in 1999 by Caltech's Jim Eisenstein, the Frank J. Roshek Professor of Physics and Applied Physics. Eisenstein's quantum liquid crystal was two-dimensional, meaning that it was confined to a single plane inside the host material—an artificially grown gallium-arsenide-based metal. Such 2-D quantum liquid crystals have since been found in several more materials including high-temperature superconductors. These are materials that conduct electricity with zero resistance at around –150 degrees Celsius, which is warmer than operating temperatures for traditional superconductors.</p><p>John Harter, a postdoctoral scholar in the Hsieh lab and lead author of the new study, explains how 2-D quantum liquid crystals behave in strange ways. "Electrons living in this flatland collectively decide to flow preferentially along the x-axis rather than the y-axis even though there's nothing to distinguish one direction from the other," he says.</p><p>Now Harter, Hsieh, and their colleagues at Oak Ridge National Laboratory and the University of Tennessee have discovered the first 3-D quantum liquid crystal. Compared to a 2-D quantum liquid crystal, the 3-D version is even more bizarre. Here, the electrons not only make a distinction between the x-, y-, and z-axes, but they also have different magnetic properties depending on whether they flow forward or backward on a given axis.</p><p>"Running an electrical current through these materials transforms them from nonmagnets into magnets, which is highly unusual," says Hsieh. "What's more, in every direction that you can flow current, the magnetic strength and magnetic orientation changes. Physicists say that the electrons 'break the symmetry' of the lattice."</p><p>Harter hit upon the discovery serendipitously. He was originally interested in studying the atomic structure of a metal compound based on the element rhenium. In particular, he was trying to characterize the structure of the crystal's atomic lattice using a technique called optical second-harmonic rotational anisotropy. In these experiments, laser light is fired at a material, and light with twice the frequency is reflected back out. The pattern of emitted light contains information about the symmetry of the crystal. The patterns measured from the rhenium-based metal were very strange—and could not be explained by the known atomic structure of the compound. </p><p>"At first, we didn't know what was going on," Harter says. The researchers then learned about the concept of 3-D quantum liquid crystals, developed by Liang Fu, a physics professor at MIT. "It explained the patterns perfectly. Everything suddenly made sense," Harter says.</p><p>The researchers say that 3-D quantum liquid crystals could play a role in a field called spintronics, in which the direction that electrons spin may be exploited to create more efficient computer chips. The discovery could also help with some of the challenges of building a quantum computer, which seeks to take advantage of the quantum nature of particles to make even faster calculations, such as those needed to decrypt codes. One of the difficulties in building such a computer is that quantum properties are extremely fragile and can easily be destroyed through interactions with their surrounding environment. A technique called topological quantum computing—developed by Caltech's Alexei Kitaev, the Ronald and Maxine Linde Professor of Theoretical Physics and Mathematics—can solve this problem with the help of a special kind of superconductor dubbed a topological superconductor.</p><p>"In the same way that 2-D quantum liquid crystals have been proposed to be a precursor to high-temperature superconductors, 3-D quantum liquid crystals could be the precursors to the topological superconductors we've been looking for," says Hsieh.</p><p>"Rather than rely on serendipity to find topological superconductors, we may now have a route to rationally creating them using 3-D quantum liquid crystals" says Harter. "That is next on our agenda."</p><p>The <em>Science </em>study, titled <a href="http://resolver.caltech.edu/CaltechAUTHORS:20170420-145037343">"A parity-breaking electronic nematic phase transition in the spin-orbit coupled metal Cd<sub>2</sub>Re<sub>2</sub>O<sub>7</sub>,"</a> was funded by the U.S. Department of Energy, the U.S. Army Research Office's Defense University Research Instrumentation Program, the Alfred P. Sloan Foundation, the National Science Foundation, and the Gordon and Betty Moore Foundation.</p></div></div></div><div class="field field-name-field-pr-links field-type-link-field field-label-above"><div class="field-label">Related Links:&nbsp;</div><div class="field-items"><div class="field-item even"><a href="http://www.caltech.edu/news/new-clues-emerge-30-year-old-superconductor-mystery-53042" class="pr-link">New Clues Emerge in 30-Year-Old Superconductor Mystery</a></div></div></div>Thu, 20 Apr 2017 00:51:43 +0000wclavin54788 at http://www.caltech.eduTwo Physicists Named Sloan Fellowshttp://www.caltech.edu/news/two-physicists-named-sloan-fellows-54178
<div class="field field-name-news-writer field-type-ds field-label-inline clearfix"><div class="field-label">News Writer:&nbsp;</div><div class="field-items"><div class="field-item even">Lori Dajose</div></div></div><div class="field field-name-field-images field-type-file field-label-hidden"><div class="field-items"><div class="field-item even"><div class="ds-1col file file-image file-image-gif view-mode-full_grid_9 clearfix ">
<img src="http://s3-us-west-1.amazonaws.com/www-prod-storage.cloud.caltech.edu/styles/article_photo/s3/SloanFoundation-Logo_0.gif?itok=8CWv6CGo" alt="Sloan Foundation logo" /></div></div></div></div><div class="field field-name-body field-type-text-with-summary field-label-hidden"><div class="field-items"><div class="field-item even"><p><a href="https://www.pma.caltech.edu/content/xie-chen">Xie Chen</a>, assistant professor of theoretical physics, and <a href="https://www.pma.caltech.edu/content/manuel-endres">Manuel Endres</a>, assistant professor of physics, have been named recipients of 2017 Sloan Research Fellowships. They are among 126 early career scholars honored this year by the Alfred P. Sloan Foundation. Each will receive $60,000 to further their research.</p><p>Chen's research is at the intersection of condensed matter physics and quantum information. Condensed matter physics studies the large-scale properties of materials starting from their miniscule components—particles such as electrons and atoms. Quantum information science investigates how quantum mechanical systems transmit information and perform computation. Chen's work examines how particles interact at the quantum level and how such interactions can enable new ways to store, manipulate, and transmit information.</p><p>"It is a great honor to receive the Sloan Fellowship," says Chen. "I am very excited and appreciative of the support to our effort in addressing fundamental questions and pursuing open-ended research directions, which can be risky but also highly rewarding scientifically."</p><p>Endres studies quantum many-body systems, which are large collections of interacting quantum particles. His experiments aim to control such ensembles, which will be essential for experimentally studying some of the outstanding mysteries of many-body systems and for developing new quantum technologies, including quantum-enhanced computing, simulation, and precision measurements.</p><p>"I am honored to receive a Sloan Fellowship," says Endres. "Physics is a 'team sport' and, therefore, I am most thankful to my colleagues who have worked with me in the past years. The Sloan Fellowship will help me and my group explore new avenues for controlling quantum many-body systems."</p><p>A full list of the 2017 Fellows is available at the Sloan Foundation website at <a href="https://sloan.org/fellowships/2017-Fellows">https://sloan.org/fellowships/2017-Fellows</a>.</p></div></div></div><div class="field field-name-field-pr-links field-type-link-field field-label-above"><div class="field-label">Related Links:&nbsp;</div><div class="field-items"><div class="field-item even"><a href="http://www.caltech.edu/news/quantum-information-meets-condensed-matter-inside-mind-xie-chen-43439" class="pr-link">Quantum Information Meets Condensed Matter: Inside the Mind of Xie Chen</a></div><div class="field-item odd"><a href="http://www.caltech.edu/content/full-circle-physics-0" class="pr-link">Full Circle Physics</a></div><div class="field-item even"><a href="http://www.caltech.edu/news/contemplating-quantum-future-49742" class="pr-link">Contemplating a Quantum Future</a></div></div></div>Tue, 21 Feb 2017 21:51:35 +0000ldajose54178 at http://www.caltech.eduCaltech Computes: Disrupting and Uniting Science and Engineeringhttp://www.caltech.edu/news/caltech-computes-disrupting-and-uniting-science-and-engineering-53359
<div class="field field-name-news-writer field-type-ds field-label-inline clearfix"><div class="field-label">News Writer:&nbsp;</div><div class="field-items"><div class="field-item even">Robert Perkins</div></div></div><div class="field field-name-field-images field-type-file field-label-hidden"><div class="field-items"><div class="field-item even"><div class="ds-1col file file-video file-video-youtube view-mode-full_grid_9 clearfix ">
<a href="/media_colorbox/13377/colorbox/en" title="" class="media-colorbox " style="" rel="" data-mediaColorboxFixedWidth="" data-mediaColorboxFixedHeight="" data-mediaColorboxAudioPlaylist="0"><div id="file-13377--2" class="file file-video file-video-youtube">
<h2 class="element-invisible">Adam Wierman - Caltech Computes - Alumni College 2016</h2>
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<img src="http://s3-us-west-1.amazonaws.com/www-prod-storage.cloud.caltech.edu/styles/grid_9/s3/media-youtube/PNFwIFensq4.jpg?itok=fyN8cOop" width="450" height="300" alt="Adam Wierman - Caltech Computes - Alumni College 2016" /> </div>
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</a><div class="field field-name-field-caption field-type-text field-label-hidden"><div class="field-items"><div class="field-item even">Adam Wierman gives the introduction to the 2016 Alumni College event.</div></div></div><div class="field field-name-credit-sane-label field-type-ds field-label-hidden"><div class="field-items"><div class="field-item even">Credit: Caltech Academic Media Technologies</div></div></div></div></div></div></div><div class="field field-name-body field-type-text-with-summary field-label-hidden"><div class="field-items"><div class="field-item even"><p>Driven by the disruptive force of computer science—which increasingly impacts how researchers work and collaborate by providing them with the ability to extract meaningful information from enormous data sets—whole new fields are developing at the intersection of science and engineering that will shape our future.</p><p>About 200 Caltech alumni, students, faculty, and friends filled the Beckman Institute Auditorium on November 12 for the Caltech Alumni Association's sold-out event, Caltech Computes: Disrupting Science and Engineering with Computational Thinking, which showcased the impact of a computational approach on a variety of fields, including biology, astronomy, and economics.</p><p>"…probability, optimization, machine learning, statistics: No matter what discipline you're in, you need these fields," the event's faculty coordinator, <a href="http://eas.caltech.edu/people/3336/profile">Adam Wierman</a>, said at the event while introducing a series of faculty speakers. Wierman is a professor of computing and mathematical sciences (CMS) in the Division of Engineering and Applied Science (EAS). "It's from this intellectual core that new fields are emerging. [For example,] when you take biology and connect it to this core, you get bioinformatics or computational genomics," he said.</p><p>Wierman, executive officer for CMS and the director of Information Science and Technology at Caltech, is leading an initiative to reenvision information science as a hub for the rest of campus.</p><p>The future of computer science at Caltech and the world in general, he noted, can be summarized by the shorthand "CS+X," as in, "What happens when you take computational thinking and combine it with some other discipline? Something new and disruptive."</p><p>In 2004, Caltech announced grants of $25 million from the Annenberg Foundation and $22.2 million from the Gordon and Betty Moore Foundation in support of this interdisciplinary initiative.</p><p>Since that time, there has been an explosion in interest in computer science—by both faculty and students. Currently more than 40 percent of the undergraduate population is majoring or minoring in computer science. Students today see the interdisciplinary nature of their advisers' research, and actively pursue the computer science skillset they will need to thrive in any career they choose, Wierman said—an ethos showcased at the Alumni Association event.</p><p> "This weekend illustrated the innovative work occurring across Caltech's campus, as well as the dedicated outreach efforts of the Caltech Alumni Association," Wierman says.</p><p>Speakers at the event included representatives from a half-dozen fields and nearly every division across campus:</p><p><strong>CS+Data</strong></p><p style="margin-left: 40px;"><a href="http://eas.caltech.edu/people/3151/profile">Pietro Perona</a>, Allen E. Puckett Professor of Electrical Engineering, whose Visipedia project is capable of distinguishing individual bird and tree species, using a combination of machine learning and expert human input. <a href="http://bit.ly/2hWyAcv">[Watch the talk]</a></p><p style="margin-left: 40px;"><a href="http://eas.caltech.edu/people/5388/profile">Yisong Yue</a>, assistant professor of computing and mathematical sciences, who is collaborating with <a href="http://eas.caltech.edu/people/2953/profile">Joel Burdick</a>, the Richard L. and Dorothy M. Hayman Professor of Mechanical Engineering and Bioengineering and JPL research scientist, to develop a prosthesis that can utilize machine learning to help patients with spinal injuries to stand again. "Every patient is unique and every injury is unique. You need it to learn on the fly," Yue said in his talk. <a href="http://bit.ly/2i6EJ9B">[Watch the talk]</a></p><p><strong>CS+Astronomy</strong></p><p style="margin-left: 40px;"><a href="http://www.astro.caltech.edu/people/faculty/George_Djorgovski.html">George Djorgovski</a>, professor of astronomy, director of the Center for Data Driven Discovery, and executive officer for astronomy in the Division of Physics, Mathematics and Astronomy. Djorgovski searches for "things that go bang in the night"—such as supernovas—by scanning enormous data sets gathered by sky surveys. "At some point, it's all ones and zeroes and it doesn't matter whether the data came from a seismograph or telescopes," he said at the event. <a href="http://bit.ly/2hWKlzB">[Watch the talk]</a></p><p><strong>CS+Biology</strong></p><p style="margin-left: 40px;"><a href="http://eas.caltech.edu/people/3135/profile">Richard Murray</a> (BS '85), the Thomas E. and Doris Everhart Professor of Control and Dynamical Systems and Bioengineering, who is creating synthetic biological machines with programming written directly into their DNA. <a href="http://bit.ly/2i6FsHJ">[Watch the talk]</a></p><p style="margin-left: 40px;"><a href="http://dna.caltech.edu/~lulu/">Lulu Qian</a>, assistant professor of bioengineering, who wants to use DNA origami to create a real-life version of "Hermione's bag" (referencing the bottomless storage of the fictional Harry Potter character's purse). <a href="http://bit.ly/2i6H0l2">[Watch the talk]</a></p><p><strong>CS+Physics</strong></p><p style="margin-left: 40px;"><a href="http://eas.caltech.edu/people/5373/profile">Thomas Vidick</a>, assistant professor of computing and mathematical sciences, who is exploring how the mysterious nature of quantum mechanics can be utilized to create unbreakable cryptography. <a href="http://bit.ly/2i6wiem">[Watch the talk]</a></p><p style="margin-left: 40px;"><a href="https://pma.caltech.edu/content/xie-chen">Xie Chen</a>, assistant professor of theoretical physics, who is developing a new model for quantum computing that overcomes the fragility of traditional approaches. <a href="http://bit.ly/2hWvjdb">[Watch the talk]</a></p><p><strong>CS+Economics</strong></p><p style="margin-left: 40px;"><a href="http://people.hss.caltech.edu/~fede/">Federico Echenique</a>, the Allen and Lenabelle Davis Professor of Economics and executive officer for the social sciences in the Division of Humanities and Social Sciences, who showed how to improve algorithms that govern how student applications are reviewed assuaged frustrated parents in the Boston public school system. <a href="http://bit.ly/2ic31e0">[Watch the talk]</a></p><p><strong>CS+Chemistry</strong></p><p style="margin-left: 40px;"><a href="http://millergroup.caltech.edu/Miller_Group/Home.html">Tom Miller</a>, professor of chemistry, whose advanced algorithms allow more precise computational models, paving the way toward more efficient and less volatile lithium-ion batteries. <a href="http://bit.ly/2i6BU8u">[Watch the talk]</a></p><p><strong>CS+Energy</strong></p><p style="margin-left: 40px;"><a href="http://eas.caltech.edu/people/3109/profile">Steven Low</a>, professor of computer science and electrical engineering, who envisions a future in which algorithms govern electric vehicle charging, reducing the need for a massive charging infrastructure. <a href="http://bit.ly/2hWDeao">[Watch the talk]</a></p><p><strong>CS+Visualization</strong></p><p style="margin-left: 40px;"> <a href="http://eas.caltech.edu/people/3197/profile">Peter Schröder</a>, the Shaler Arthur Hanisch Professor of Computer Science and Applied and Computational Mathematics, whose discussion of the application of algorithms from quantum mechanics to the generation of computer-simulated fluids gave the audience a look "under the hood of what makes Hollywood fly," he said. <a href="http://bit.ly/2gYR4Hu">[Watch the talk]</a></p></div></div></div><div class="field field-name-field-pr-links field-type-link-field field-label-above"><div class="field-label">Related Links:&nbsp;</div><div class="field-items"><div class="field-item even"><a href="http://bit.ly/2hQkBW0" class="pr-link">Full playlist</a></div></div></div>Tue, 20 Dec 2016 18:35:55 +0000rperkins53359 at http://www.caltech.eduPioneering Physics Show The Mechanical Universe Now on YouTubehttp://www.caltech.edu/news/pioneering-physics-show-mechanical-universe-now-youtube-53331
<div class="field field-name-field-subtitle field-type-text field-label-hidden"><div class="field-items"><div class="field-item even">The 1980s series was based on the Physics 1a and 1b courses developed by David Goodstein</div></div></div><div class="field field-name-news-writer field-type-ds field-label-inline clearfix"><div class="field-label">News Writer:&nbsp;</div><div class="field-items"><div class="field-item even">Jon Nalick</div></div></div><div class="field field-name-field-images field-type-file field-label-hidden"><div class="field-items"><div class="field-item even"><div class="ds-1col file file-image file-image-jpeg view-mode-full_grid_9 clearfix ">
<img src="http://s3-us-west-1.amazonaws.com/www-prod-storage.cloud.caltech.edu/styles/article_photo/s3/Mechanical%20Universe.jpg?itok=n8fR6sIC" alt="Image of spaceships and vector math symbols" /><div class="field field-name-field-caption field-type-text field-label-hidden"><div class="field-items"><div class="field-item even">The show often used computer animation in a groundbreaking way to visualize mathematical manipulations.</div></div></div></div></div></div></div><div class="field field-name-body field-type-text-with-summary field-label-hidden"><div class="field-items"><div class="field-item even"><p>The critically acclaimed television series <em>The Mechanical Universe… And Beyond</em>, created at Caltech and broadcast on PBS from 1985-86, is now available in its entirety on YouTube thanks to the efforts of Caltech's Institute's Information Science and Technology initiative.</p><p>The series was based on the Physics 1a and 1b courses developed by David Goodstein, the Frank J. Gilloon Distinguished Teaching and <span style="font-family: Helvetica; font-size: 13.2px;">Service Professor and Professor of Physics and Applied Physics, Emeritus</span>. It covers topics spanning the scientific revolution begun by Copernicus through quantum theory.</p><p>Each episode opens and closes with Goodstein lecturing to his freshman physics class in 201 E. Bridge, providing philosophical, historical, and often humorous insight into the day's topic. The show also contains hundreds of computer animation segments, created by JPL computer graphics engineer James F. Blinn, as the primary tool of instruction. Dynamic location footage and historical re-creations are also used to stress the fact that science is a human endeavor.</p><p>Mathieu Desbrun, the John W. and Herberta M. Miles Professor of Computing and Mathematical Sciences, says Caltech was eager to feature the course on its YouTube site because it has been used for decades around the world as a teaching aid, underscoring one of the ways the Institute continues to have an impact disproportionate to its size.</p><p>Although the series was designed as a college-level course, "thousands of high school teachers across the US came to depend on it for instructional and inspirational use," Goodstein says. "The level of instruction in the US was, and remains, abysmally low, and these 52 programs filled a great void."</p><p>The show retains its impact and relevance, partly because "Newton's three laws are still the law of the land," he says—as are other subjects addressed in the series such as relativity, electromagnetic theory, and quantum mechanics.</p><p>Blinn says the series was designed to be rigorous and engaging and used computer animation in a groundbreaking way to visualize mathematical manipulations. Creators of the series referred to the animation as "algebraic ballet," with terms and visual metaphors dancing around the screen to show operations like cancellation and differentiation. "The availability of technology made it so that the developers of the series could see their ideas realized," he says.</p><p>The use of Blinn's computer animations—a rare and expensive technology at the time—made it "legendary," Desbrun says. "<em>The Mechanical Universe</em> is a piece of Caltech history and a source of pride."</p><p>The series can be found online at <a href="http://bit.ly/2gvNAA3">http://bit.ly/2gvNAA3</a>.</p></div></div></div>Fri, 16 Dec 2016 21:50:21 +0000jnalick53331 at http://www.caltech.eduGarnet Chan Talks Quantum Chemistry and Chinese Foodhttp://www.caltech.edu/news/garnet-chan-talks-quantum-chemistry-and-chinese-food-53248
<div class="field field-name-news-writer field-type-ds field-label-inline clearfix"><div class="field-label">News Writer:&nbsp;</div><div class="field-items"><div class="field-item even">Whitney Clavin</div></div></div><div class="field field-name-field-images field-type-file field-label-hidden"><div class="field-items"><div class="field-item even"><div class="ds-1col file file-image file-image-jpeg view-mode-full_grid_9 clearfix ">
<img src="http://s3-us-west-1.amazonaws.com/www-prod-storage.cloud.caltech.edu/styles/article_photo/s3/Chan-Garnet-FACULTY_CCE-7622-NEWS-WEB.jpg?itok=5578T5Zz" alt="Garnet Chan" /><div class="field field-name-field-caption field-type-text field-label-hidden"><div class="field-items"><div class="field-item even">Garnet Chan, Bren Professor of Chemistry at Caltech</div></div></div><div class="field field-name-credit-sane-label field-type-ds field-label-hidden"><div class="field-items"><div class="field-item even">Credit: Caltech</div></div></div></div></div></div></div><div class="field field-name-body field-type-text-with-summary field-label-hidden"><div class="field-items"><div class="field-item even"><p><a href="http://cce.caltech.edu/content/garnet-chan">Garnet Chan</a>, Bren Professor of Chemistry, recently moved to Pasadena from New Jersey, where he was a professor at Princeton University for the past four years. Chan's specialty is quantum chemistry, a field pioneered at Caltech by the late Linus Pauling to understand the behavior of molecules. Raised in Hong Kong, Chan earned his bachelor's degree (1996) and PhD (2000) from the University of Cambridge, then was a Miller Fellow at UC Berkeley before taking a faculty position at Cornell University.</p><p>Chan sat down with us to discuss his move to Pasadena and his excitement over the Chinese culinary delights the area has to offer—and to answer a question he's heard before: What exactly does a quantum chemist do?</p><h3>How do you describe the big picture of what you do?</h3><p>Broadly speaking, I'm a theorist, and I'm interested in going from the very simple equations of quantum mechanics—which are the fundamental equations of nature, the most basic equations we know about the world—to the actual behavior of molecules and materials and real matter that we can touch around us. It's a discipline that involves finding computer algorithms that allow us to simulate these equations, at least approximately.</p><p>What makes me a quantum chemist as opposed to another kind of researcher working with quantum mechanics is that the problems I'm interested in are the ones that chemists study. These can be very concrete things like what steps are involved when an enzyme catalyzes a reaction, or what makes a material absorb a specific frequency of light. Basically, we are trying to simulate complex chemistry.</p><h3>What problems are you specifically working on?</h3><p>One problem we are working on is the problem of high-temperature superconductivity, which has been a mystery for 30 years. Superconductivity is the name given to the phenomenon where if you lower the temperature sufficiently in a material, you'll reach a point where the resistance to electric current all of a sudden goes to zero. We then say that the material is superconducting. In a certain class of materials called high-temperature superconductors, you do not have to lower the temperature very much. You still have to lower the temperature to minus 140 degrees Celsius. It seems cold, but that's equivalent to 130 to 140 Kelvin, and most materials are only superconducting up to about 10 Kelvin. Even though high-temperature superconductors were discovered 30 years ago, we still don't know how they work.</p><p>I have kind of an attachment to this problem because I like problems that people have banged their heads on for decades, and in many cases given up on solving. I think many people would agree that this is probably one of the single most perplexing questions about materials. The real thing that has changed in the last 30 years is the development of new computational tools for quantum mechanics. You used to solve problems by having some inspired guess. Our hope now is that we don't have to make such an inspired guess because we can get at least some of the way there by computation.</p><p>I've in some sense worked 15 years trying to build up a set of tools that can address the different challenges involved in simulating these materials. We've recently achieved success in simulating simplified models of the materials. By simplification, one can think of it as like trying to simulate the planets in the solar system, but with some of the planets taken out. We can now can simulate the models to very high precision, and you can see behavior very similar to the real high-temperature superconductors. This gives us confidence that we can soon understand what is happening in the real materials.</p><h3>Do you have any other projects?</h3><p>Another one of my interests is related to the biological mechanism by which enzymes "fix" nitrogen. Most of the nitrogen on Earth is in the air as nitrogen gas [N<sub>2</sub>], but humans can't process nitrogen gas. Instead, we get much of our nitrogen indirectly from fertilizer—or from bacteria. Certain bacteria have an enzyme that naturally "fixes" nitrogen, which means that it is converted into ammonia or related compounds that fertilize plants. The plants make amino acids, and we eat the plants—or animals eat the plants and we eat the animals. In the end, the nitrogen gets into us.</p><p>What makes the biological process so fascinating is that it is able to proceed under ambient biological conditions, while industrial fertilizer production, via the Haber process, proceeds at high temperatures and pressures, and consumes enormous amounts of energy. This means that the biological enzymes are doing some very clever chemistry. We hope to unravel the details of this process using the principles of quantum mechanics. We've recently uncovered some unexpected behavior of the electrons in these enzymes. Perhaps the answer to how they work lies there!</p><h3>What happens after you simulate the chemistry for reactions like this?</h3><p>The results of computational chemistry simulations are used by many chemists, not just theorists like me. In fact, these days a very large number of experimental papers have quantum chemical calculations in them to help interpret the results—in this sense, there is a very healthy interplay between theory and experiment. However, I see the role of our simulations as having impact beyond the specific problems that we choose to study. That is because the tools that we are building to perform our simulations help push the frontier of the types of chemistry and reactions that people can study. Eventually, these tools will be usable by all chemists, and I hope they can be used to study all of chemistry.</p><p>Quantum chemistry has always evolved to make new tools to answer more and more complicated questions. In the beginning, in the 1920s and 1930s, people were mainly studying atoms. Later, they studied molecules and what holds them together—Linus Pauling, who was a professor here, started this type of work. These days we are working at a frontier where the tools are being developed to study the most complex problems of biology and materials.</p><h3>What are you most excited about in coming to Caltech?</h3><p>I'm completely sold on this place. People here are focused on science, so this is exactly the right place for me. I also like the scale. It's so small that you really feel like you're in some family. Certainly the chemistry department feels like a very tight-knit community.</p><h3>What do you like about Southern California?</h3><p>I think there's a reason why so many people live in Southern California. It doesn't get better than this. You have great weather. There's lots of good food. People complain about traffic, but I lived in New Jersey and traffic there is terrible. Also, this area of the country has probably the best Chinese food. There are hundreds of good Chinese restaurants in the cities of San Gabriel, Monterey Park, and Alhambra. Food is such a big part of all cultures, but certainly a big part of Chinese culture, so that's a big plus.</p></div></div></div>Fri, 09 Dec 2016 22:28:29 +0000wclavin53248 at http://www.caltech.eduManipulating Quantum Orderhttp://www.caltech.edu/news/manipulating-quantum-order-52987
<div class="field field-name-news-writer field-type-ds field-label-inline clearfix"><div class="field-label">News Writer:&nbsp;</div><div class="field-items"><div class="field-item even">Kathy Svitil</div></div></div><div class="field field-name-field-images field-type-file field-label-hidden"><div class="field-items"><div class="field-item even"><div class="ds-1col file file-image file-image-png view-mode-full_grid_9 clearfix ">
<img src="http://s3-us-west-1.amazonaws.com/www-prod-storage.cloud.caltech.edu/styles/article_photo/s3/rosenbaum-electrons-magnetic_moments.png?itok=FsnMRypD" alt="graphic showing electrons and magnetic moments of atoms" /><div class="field field-name-field-caption field-type-text field-label-hidden"><div class="field-items"><div class="field-item even">The electrons (red and blue clouds) and intrinsic magnetic moments of atoms (arrows) can work together to induce superconductivity under the right conditions. The application of pressure can help tune those interactions.</div></div></div><div class="field field-name-credit-sane-label field-type-ds field-label-hidden"><div class="field-items"><div class="field-item even">Credit: Caltech</div></div></div></div></div></div></div><div class="field field-name-body field-type-text-with-summary field-label-hidden"><div class="field-items"><div class="field-item even"><p>Cool a material to sufficiently low temperatures and it will seek some form of collective order. Add quantum mechanics or confine the geometry and the states of matter that emerge can be exotic, including electrons whose spins arrange themselves in spirals, pinwheels, or crystals.</p><p>In a recent pair of publications in <em>Nature Communications</em>, teams led by Caltech's <a href="http://www.caltech.edu/content/about-president-rosenbaum">Thomas F. Rosenbaum</a>, professor of physics and holder of the Sonja and William Davidow Presidential Chair, report how they have combined magnetic fields and large pressures to not only induce these states at ultra-low temperatures, but also to nudge them between competing types of quantum order.</p><p>Rosenbaum is an expert on the quantum mechanical nature of materials—the physics of electronic, magnetic, and optical materials at the atomic level—that are best observed at temperatures near absolute zero. In the first of the two papers, published in June and led by Sara Haravifard, now on the faculty at Duke University, the team squeezed a collection of magnetic quantum particles in a pressure cell at temperatures near absolute zero and at magnetic fields more than 50,000 times stronger than the earth's field, and discovered the formation of new types of crystal patterns. The geometry of these crystal patterns not only reveals the underlying quantum mechanics of the interactions between the magnetic particles, but also bears on the kinds of collective states allowed for atomic systems, such as those that flow without friction.</p><p>In the work in the second paper, published in October and led by Caltech graduate student Yishu Wang and Argonne scientist Yejun Feng, Rosenbaum and colleagues also investigate how materials balance on the knife edge between different types of quantum order. In this case, however, the researchers focus on the relationship between magnetism and superconductivity—the complete disappearance of electrical resistance—and how those properties relate to one another when the material changes state under the pressures achievable in a diamond anvil cell. </p><p>The researchers used the Advanced Photon Source at Argonne National Laboratory to study the magnetic properties of the transition metal manganese phosphide (MnP) to see how it might be possible to manipulate the ordering of the spins—the intrinsic magnetic moments of the electrons—to either enhance or suppress the onset of superconductivity.</p><p>Superconductivity is a state in a material in which there is no resistance to electric current and all magnetic fields are expelled. This behavior arises from a so-called "macroscopic quantum state" where all the electrons in a material act in concert to move cooperatively through the material without energy loss.</p><p>Rosenbaum and his colleagues delineated a spiral pattern of the magnetic moments of the electrons in MnP that could be tuned by increasing pressure to induce superconductivity. Here again the particular geometry of the magnetic pattern held the key to the ultimate state that the material reached. "The experiments reveal manifest opportunities to find new low-energy states via substitutions for manganese and phosphorus with neighboring elements from the periodic table such as chromium and arsenic. The taxonomy of allowable quantum states and the ability to manipulate them unites approaches across quantum physics and technology," Rosenbaum says. </p><p>The first paper, <a href="http://resolver.caltech.edu/CaltechAUTHORS:20160627-133636332">"Crystallization of spin superlattices with pressure and field in the layered magnet SrCu<sub>2</sub>(BO<sub>3</sub>)<sub>2</sub>,"</a> was published on June 20, 2016. Coauthors include Daniel M. Silevitch<strong>, </strong>research professor of physics at Caltech. Work at Caltech was supported by the National Science Foundation. The research in the second paper, entitled <a href="http://resolver.caltech.edu/CaltechAUTHORS:20161011-134922256">"Spiral magnetic order and pressure-induced superconductivity in transition metal compounds"</a> and published on October 6, was funded at Caltech by a U.S. Department of Energy Basic Energy Sciences award.</p></div></div></div>Tue, 15 Nov 2016 01:17:19 +0000rbasu52987 at http://www.caltech.edu